Graphene is electrically, mechanically, and chemically stable and outstanding, and also, the graphene is an excellent conductor capable of moving electrons about 100 times faster than silicon and carrying about 100 times more electric current than copper. Thus, a lot of research on production and application of graphene has been carried out. By way of example, Korean Patent Application No. 10-2011-0040229 describes “Graphene thin film by electrostatic spraying deposition and manufacturing method thereof”. However, for the present, a method for controllable mass production of graphene needs to be developed, and also, a problem of low production yield and high cost needs to solved.
Recently, in order to solve problems incurred when graphene is mass-produced by conventional methods, there has been developed a method for producing a chemically reduced graphene oxide (hereinafter, referred to as “rGO”) having a semiconducting property. By way of example, there has been developed a method in which oxidized graphite is produced to a graphene oxide (hereinafter, referred to as “GO”) nano-sheet and the GO is reduced to produce an rGO of high quality.
An rGO thin film including a monolayer or double layers has a semiconducting property, and an rGO film thicker than the rGO thin film has a semimetallic property. Further, the rGO thin film has a low sheet resistance and a high transparency. An rGO thin film can be used for improving sensitivity within a biosensor due to its semiconducting property.
A biosensor has been used in various fields of industry. In order to improve performance of the biosensor, it is necessary to use a sensitive element having a high sensitivity. By way of example, there is a research in which a gold nanoparticle (hereinafter, referred to as “AuNP”) physically included in an organic layer or physically attached onto the organic layer is used as a sensitive element in order to improve sensitivity of a biosensor.
However, if the AuNP is physically included in the organic layer or attached onto the organic layer, it is difficult to uniformly disperse the AuNP in the organic layer and a life span of the biosensor can be reduced. Further, it is difficult to find out whether “charging effect” directly related to performance as a sensitive element can be shown due to presence of the AuNP, presence of the organic layer, or presence of both the AuNP and the organic layer, and, thus, it is difficult to make a technical improvement.